The opposite of SNAFU. Situation Terrific Feelin' Upbeat! First used by mid-western housewives at social gatherings such as picnics, little-league games and bingo night. The term is gradually spreading across the US and makes for confusing if not interesting web chat.

LUANN: How's the bake sale goin' Judy?
JUDY: STFU Luann! We've already met our sales goal, have run out of gingersnaps, and are about to sell our last box of cupcakes!

an irrational response to your mother's comments that make more sense than your brain can accommodate
comfortably

"I thought we were going to spend the day together for Father's Day"
"Your Dad has been here all day, he worked in the yard for hours and just went to hit golf balls with your brother, they will be back by six"
"Oh, so I have been here all day, but he can go off with my brother" some more words of unkindness and then:
stfu, i am leaving
ridiculous.